This invention in general concerns improved method and apparatus for determining physical characteristics of plants, and in particular concerns mapping of a plurality of foliar volumes situated in a given orientation such as in the case of orchard trees. Further aspects of the invention concern method and apparatus for controlling the application of various materials based on the detected plant characteristics.
Modern agricultural methods have introduced the use of a variety of practices resulting in products of both improved quality and increased quantity, i.e. yield. While some of such practices generally concern the area of land management (for example, the control of land erosion and soil misuse through particular planting and cultivation regimens), others have been generally concerned with the application of various materials to the soil and/or the in-ground crops. For example, various soil enhancers such as granular fertilizers, limes, and other products may be used particularly during early stages of plant development to promote initial growth in the plants. As plants grow and mature, other types of materials, such as liquid chemicals may be applied to the plant surfaces for controlling plant diseases and for eradicating pests from the crops.
One example of cultivated crops which commonly receive considerable application of various chemical products is in the area of orchard trees. Orchards are conventionally arranged in equidistant rows of trees, with sufficient room between such rows for tractor-drawn sprayers, harvesters, and the like. Throughout the productive life of such trees, the spaces between the rows may be used to provide access for equipment to initially plant and fertilize the trees, later spray the trees, and ultimately harvest their production.
While modernization has unquestionably resulted in tremendous strides in agricultural production, the ever-increasing cost of such practices and constraints thereon (such as government controls concerning the use of agricultural chemicals) have been cause for considerable research directed towards improving the efficiency of agricultural material application, particularly liquid chemical application. Various plant and animal science efforts (such as in the specific fields of agronomy, entomology, and horticulture) have led to the production of advanced materials and improved chemical control methods. However, the essential mechanics of actually applying such chemicals onto target crops continues to remain as primarily engineering problems.
The primary task of an ideal or optimal spraying system is to deliver uniformly and exclusively to a target area a precise specified amount of material. Such object is less of an engineering problem in "perfect" environments, i.e. where the target morphologies are well defined and non-variable. An industrial spray system (for example, successive painting of identically-shaped objects) can be controlled to achieve optimal performance, that is where essentially all material discharged reaches a desired target.
Unlike tightly-controlled industrial spray applications, agricultural spray systems must operate in highly adverse environments where the target geometries are poorly defined, as well as being highly variable. In many instances, the application rate of a given system is merely set at the start of a spraying season and left unchanged. Such an approach has the obvious drawback that the effective application rate of the material varies (uncontrollably) due to normal plant growth or simply due to variations within a given field. Target areas more dense than the nominal density corresponding with the selected application rate are under-applied with the subject materials; conversely, target areas less dense than the nominal density receive an excess application of material.
Particularly in the area of pest control chemicals, an operator may seek to maintain control in an entire target region by selecting the nominal application rate based on the most dense target areas thereof. Such practice obviously leads to even greater over-application of pest control chemicals, thereby increasing both the chemical product and application cost to the producer, while further introducing excess chemicals into the environment with virtually no benefit.
Various sprayer control systems have been developed which attempt to improve over-all efficiency of chemical application by adjusting sprayer outputs based on sensed target crop characteristics. For example, one type of commercially available control system adjusts spray output based on ground speed variations of the sprayer. However, since no characteristics of the crops themselves are sensed in such systems, a necessary assumption is made that the crop area is homogeneous across the spray area. Such assumption would rarely if ever be accurate for many applications.
Yet another type of sprayer control system senses the presence of target plants or crops, and activates the spray output accordingly. Such control systems physically detect the presence of target plants using various probes and intermittently control the spray systems responsive to probe results. A system made by the Roper Growers Cooperative, of Winter Garden, Fla., activates spray nozzles in different vertical zones based on ultrasonic sensing of the presence of trees in corresponding vertical sensing zones. Essentially, the height of a given target tree is estimated with a plurality of vertical sensors, and then used to control turn-on of the corresponding manifold segments.
Efficient spray control for orchard crops is particularly difficult to achieve in comparison with row crop chemical application because the orchard target areas are often significant distances away from sprayer outlets. In row crops, spray nozzles may be cantilevered with a horizontal boom to project over the crops and point literally directly down thereon at close range.
Furthermore, for a given unit of land area, orchard crops have much larger volumes of foliage (i.e. target areas) than relatively smaller row crops. Also, such foliage volume can considerably vary in both height and width characteristics of target crops, thereby presenting rigorous criteria for an optimal application orchard sprayer control system. Due to such considerable variation in target volumes, this invention recognizes that a system approaching an actual measurement of the amount of target foliage present is a highly desireable basis for sprayer control.
Another approach to sensing target trees was set forth in a proposal by McConnell et al. (1983) based on research efforts conducted at the West Virginia University. It was proposed by McConnell et al. that a vertical mast of ultrasonic range transducers could be used to measure and record tree extension outward from the tree trunk. By using a plurality of vertically-displaced sensors, a vertical scan could be obtained and used to estimate the tree foliage volume. While no laboratory or field tests were conducted by McConnell et al., they theorized that such tree foliage volume estimates could be applied as a management tool for possible growth monitoring of an entire tree row or even a given block of trees, as well as for production predictions.
It was also theorized that the tree foliage volume estimates could be used to adjust chemical application rates, although concerns were expressed over how such theory could be applied to an actual practical system. One concern was that ultrasonic beam pattern divergence would lead to unacceptable performance levels, while overall system timing and data storage would be additional sources of practical problems. In particular, McConnell et al. proposed to accomplish vertical scanning under the control of a computer, and store echo data in the computer's memory. Even McConnell et al. recognized drawbacks of their proposed computer-directed detection system by calculating an upper limit on tractor speed of 1.2 meters per second, based on scan time of the transducers in consideration of internal set-up time of his proposed pulse generation electronics, and the rate at which the computer could direct and handle the overall operation and make necessary calculations. Without offering any further solutions to these drawbacks, McConnell flatly stated that parallel measurements are necessary to obtain either faster data gathering speed or greater detection resolution. It was further specifically concluded that the ultrasonic ranging system presented a challenging problem because the ultrasonic transducers which were utilized (which were commercially available from Polaroid Corporation) were not adequate for use in their theorized system.
The general purpose of simple intermittent or other more sophisticated spray application control systems is to eliminate at least a portion of the excessive or over-applied materials. However, another problem faced by growers (particularly large orchard producers) concerns excess un-applied materials. Typically, an air-blast type orchard sprayer includes a 300-500 gallon tank, in which an active chemical ingredient is pre-mixed with water or some other carrier for application to target trees. Any unused portion of the tank contents often must be disposed of in accordance with environmental hazardous waste disposal requirements, for example such as specialized burying of remaining products.
One proposed alternative involves a concept known as direct injection, in which the spray carrier (e.g. water) and the active chemical ingredient are kept separated until immediately before entry into the spray nozzle, which can greatly reduce (if not eliminate) the excess pre-mixed spray which is subject to waste and environmental hazard disposal requirements. However, this proposed concept has not been effectively applied in the field because various systems for attempted practice of the concept have proven problematic. For example, one known metering injection pump (for the active ingredient) has been determined to have relatively lengthy inherent time delays (such as 4.8 to 16.1 seconds) associated with the variable concentration control system between the initiation of metering pump adjustment and the attainment of an acceptable spray concentration error (for example, less than 10%). At 6.4 km/hr., from 8.8 to 28.7 meters would be covered by the sprayer during such time delay period. Thus, the concept of direct injection has not been used to full benefit, and has not generally heretofore been attempted with systems where target morphology information was directly sensed.
Yet another problem concerning the development of practical orchard spraying systems for optimal application of chemicals is linked with the air-blast type of sprayers themselves frequently used for orchard spraying. In contrast, row crop spraying normally results in droplet deposition downward onto the target. However, in air-blast spraying, the pesticide droplets are entrained in high-velocity, high-volume air-jets, with resulting droplet transport mechanics differing greatly from the well-understood and relatively simple mechanics of row crop spraying. Additionally, as mentioned above, the distance between target areas and sprayer outlets in orchard spraying is usually increased, which correspondingly increases the probability of droplet evaporation or drift from the target area. Such complexity of droplet transport geometry, combined with the ever-present variability of ambient wind velocity, relative humidity and temperature, makes theoretical analysis of orchard spraying very difficult. Accordingly, relatively little theoretical information is available relative air-blast sprayer deposition which could be usefully incorporated into design criteria for an orchard sprayer for optimal application.
In addition to the foregoing practical engineering and theoretical difficulties as well as hazardous waste constraints, the economic perspective of orchard spraying suggests the considerable need for optimal application of chemicals. Studies of the costs of chemical applications (including material, equipment, and labor) have been estimated to represent over 50% of the total production cost for some orchard crops, such as peaches and apples. Not only would provision of an optimal chemical application method and system obviously reduce the cost of spray materials, but a reduction in the volume of applied chemicals would result in each load of material in the sprayer covering an increased orchard area. Presently, much time is consumed in traveling to a supply area to refill a sprayer. Thus, a corresponding decrease in the amount of such time would result in a reduction in equipment and labor costs associated with spraying.